A top aide to Governor Chris Christie on Thursday told the New Jersey panel investigating lane closures on the George Washington Bridge that she had no prior knowledge of, or participation in, the incident that sparked a political firestorm.

Regina Egea, who oversaw the Christie administration's relations with the Port Authority of New York and New Jersey, was among the first gubernatorial staffers to get word of the September 2013 lane closures, after being forwarded a strongly worded email from the authority's executive director that called the closures illegal.

The controversy that local tabloids dubbed Bridgegate has proved embarrassing for Christie as he considers a 2016 run for the White House, although he has denied knowing about the incident at the time or being involved.

Egea, who is now Christie's incoming chief of staff, said she chalked the email up to an ongoing dispute between appointees from New York and New Jersey.

"My assessment, was that it seemed consistent with the tension between them," Egea said.

Egea's testimony came as panel members expressed concern that the inquiry into the scandal was losing steam.

They said the pace of the probe into the massive four-day-long traffic disruption had slowed to a crawl because potential witnesses had refused to cooperate.

The panel, formed in January, has interviewed just five of the 13 people it had planned to question.

In addition, the U.S. Attorney's Office for New Jersey asked the committee to delay interviews with key witnesses to avoid interfering with the criminal investigation, committee members told Reuters.

"It leaves us with very slim pickings, in terms of witnesses," said Assemblywoman Amy Handlin, a Republican on the committee, which is controlled by Democrats.

The shutdown in Fort Lee, New Jersey, of access lanes to one of the nation's busiest bridges caused hours-long snarls that delayed school buses, ambulances and commuters. Critics have alleged the closures were orchestrated by Christie's allies to retaliate against Fort Lee's Democratic mayor for failing to endorse the Republican governor's re-election bid.

The New York Times reported last month that a second bridge investigation linked to Christie had been launched, focusing on possible securities law violations involving the Pulaski Skyway bridge.